A number of supports for motion-picture or television cameras are known from motion-picture and television technologies, such supports having fluid-operated special heads that allow both horizontal and vertical motions to be obtained with continuity and without vibrations, and that are able to give rise to resistance forces variable according to the type and the sizes of the camera employed.
It is already well known how to obtain damping members for fluid-operated heads through the employment of friction disks of different materials, such disks being dry or lubricated, and being pressed against one another so as to give rise to a force resisting the motion.
Moreover, the adjustment effect of the angular shifts can be obtained through a system of flywheels which are driven through rolling friction, so that both a constant force resisting the motion and a positive or a negative velocity gradient are simulataneously obtained.
A further technological development of such systems occurred with the introduction of heads for application to supports for motion-picture or television cameras that employed quite a different damping principle with respect to the preceding supports.
Such a system adopted by O'Connor and disclosed in a number of patents and so developed as to be best adaptable to employment with motion-picture and television cameras, essentially consists in causing a surface to move with respect to another surface with the interposition of a high density grease capable of giving rise to a force resisting the motion and having the characteristics of continuity, as well as of absence of vibrations and noise.
One such system may consist of a cylindrical cavity containing a rotary cylinder with the interposition of a silicone grease.
In order to obtain resisting forces variable during operation while keeping the constraint of giving rise to angular shifts at various speeds. O'Connor introduced the system consisting of a steel band adhering to a metal cylinder covered with a cork lamina with interposition of a silicone oil so that variable resistance forces were obtainable by varying the pressure of the steel band.
A further development in the technology of fluid-operated heads consists in the production of variable resistance forces through the adoption of a device, similar to a brake, which comprises two shoes coated with cork within a silicone oil bath that give rise to variable resistance forces through expansion within the cylinder.
The employment of a special head is also known from a further development of techniques concerning said fluid-operated heads, such special head comprising two series of disks submerged in a silicone fluid bath in which the first series of disks, which is kept locked with respect to the second series, the latter engaging with the first series in a comb-like way, gives rise to resistance forces that are variable as a function of the number of disks in question.
This type of damping member operating on disks submerged in a silicone fluid bath in which the change in the magnitude of the damping force is obtained by locking pairs of disks in a proportional way, has the drawback of requiring a remarkable amount of fluid to warrant the total immersion of all parts and a corresponding employment of the fluid itself.
Moreover, the fact that both the disks and the locking systems for selecting the modules are submerged in the silicone fluid bath makes the maintenance operations difficult to perform.
Finally, a further drawback which is connected to the particular structure of the damping member is that the adjustments of the magnitude of the vertical and the horizontal motions are limited to a predetermined number of positions.
In order to overcome such drawbacks, it has been suggested that the damping member be provided with a series of modules of different powers in which a proportional number of action and reaction disks is grouped, such disks operating in different possible combinations in order to give rise to different resistance forces.
This type of modular device applied both to the vertical and to the horizontal shifts as disclosed in the German Patent No. 2,657,692, consists essentially of a module provided with two series of disks which can be connected respectively to the shaft and to the stationary portion or the stator of said head, such disks being of outside and inside diameters of such sizes as to become reciprocally engaged in a comb-like way and being closed at their ends by plates of a greater thickness, wherein the seal against the leak of the silicone grease is obtained by exerting an axial compression on the two sets of disks and by means of clamping devices arranged along the circumference.
The damping effect in such modules is obtained as a result of friction forces between the different surfaces of the disks with the interposition of grease, such friction forces being thus distributed over the whole surface of the disks of the first and of the second set.
One of the major drawbacks connected to such a construction of the modular damping members consists essentially in the structural complexity of the members themselves, as well as in the need for different materials to be used for the various component members, and in the particularly lengthy assembling operation, not to mention the significant increase in the cost of manufacture.
Accordingly, it is quite clear that there is a need for a modular-element damping member for fluid-operated heads that overcomes the drawbacks arising from the construction and assembly of conventional members, through the reduction of the number of materials employed, the simplification of the assembling procedure and the employment of a control and adjustment system of the amount of fluid supplied in each modular element.